Move local noop waker to local_waker feature flag

Co-authored-by: zachs18 <[email protected]>

Author: eholk

Diff for: library/core/src/task/wake.rs

@@ -863,8 +863,7 @@ impl LocalWaker {
     /// ```
     #[inline]
     #[must_use]
-    #[stable(feature = "noop_waker", since = "CURRENT_RUSTC_VERSION")]
-    #[rustc_const_stable(feature = "noop_waker", since = "CURRENT_RUSTC_VERSION")]
+    #[unstable(feature = "local_waker", issue = "118959")]
     pub const fn noop() -> &'static LocalWaker {
         const WAKER: &LocalWaker = &LocalWaker { waker: RawWaker::NOOP };
         WAKER